JP3339180B2 - Obstacle detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an obstacle detecting apparatus which detects infrared rays emitted from an obstacle having a surface temperature higher than the temperature of the outside air and identifies the presence of the obstacle.

[0002]

2. Description of the Related Art An obstacle detecting device which detects infrared rays emitted from an obstacle having a surface temperature higher than the temperature of the outside air and identifies the presence of the obstacle is arranged on the front of a vehicle.
Research has been conducted on a safety device that detects a preceding vehicle or a pedestrian, gives an alarm to a driving driver, or activates an automatic deceleration program in a car.

An example of a conventional obstacle detecting device is disclosed in Japanese Utility Model Laid-Open No. 3-6.
No. 7947. Here, the infrared light converged by the lens disposed at the tip of the lens barrel enters the infrared sensor disposed at the back of the lens barrel. The outer surface of the lens barrel is directly exposed to various external heat sources. When sunlight enters the lens barrel and the inner surface is temporarily exposed to sunlight, a local temperature rise occurs.

[0004]

Problems to be Solved by the Invention
In the obstacle detection device, if the temperature of the lens barrel or lens rises locally due to an external heat source or the incident light of sunlight, the temperature rise will cause unnecessary infrared radiation for several seconds. Source. Then, the identification means may erroneously determine that the noise signal generated by the unnecessary infrared rays on the detection element is due to an external obstacle.

When an obstacle detecting device is mounted on a vehicle, it is necessary to consider that the air temperature around the vehicle changes every moment. When the vehicle suddenly enters a tunnel while traveling on a road surface exposed to direct sunlight, the internal temperature of the obstacle detection device cannot uniformly follow a rapid change in the air temperature. If a high temperature portion is formed in the lens barrel or the condensing optical system that cannot follow the temperature change of the outside air temperature, the infrared radiation radiated from the high temperature portion also becomes a noise signal, thereby erroneously determining the obstacle by the identification means.

Incidentally, one method of increasing the sensitivity of the obstacle detection device is to increase the intensity of infrared rays focused on the detection element by increasing the diameter of the lens barrel. However, with a lens barrel having a large diameter, it is no longer possible to uniformly control the temperature of the entire barrel only by conducting heat. In addition, the variation in the temperature of each part of the lens barrel similarly causes the detection element to output a noise signal, thereby causing the identification unit to erroneously determine an obstacle. Furthermore, since the heat capacity of the lens barrel increases due to the increase in diameter and the wall thickness that maintains strength, the amount of infrared radiation radiated from the part that cannot follow changes in the environmental temperature also increases, and a large increase in the sensitivity due to the increase in diameter increases. A noise signal is formed.

Therefore, a special cooling device is provided to cool the lens barrel and the reflecting mirror, and the level of infrared rays generated by the lens barrel and the reflecting mirror is greatly reduced to solve the problem of noise signals.
However, the cooling device increases the size of the obstacle detection device, complicates the mounting structure, increases power consumption, and requires an additional heat insulating structure and countermeasures against condensation due to cooling.

The present invention provides an obstacle detecting device in which the temperature of the lens barrel and the condensing optical system quickly follows the temperature of the outside air, and the sensitivity and reliability can be improved without relying on a special cooling device or the like. The purpose is to do.

[0009]

The obstacle detecting means of the present invention comprises: a detecting element for detecting the intensity of infrared rays; a converting means for forming infrared intensity information from an output of the detecting element;
A lens barrel and a focusing optical system that guides infrared light taken from outside to the detection element and inputs the light in a focused state, and a temperature detecting unit that detects outside air temperature and outputs outside temperature information,
An identification means for determining an obstacle based on the intensity information and the outside air temperature information.In the obstacle detection device, the detection element thermally connects the cold junction to the lens barrel, and The thermopile element is a thermopile element that generates an infrared intensity output, and has a heat exchange structure that exchanges external air with the lens barrel.

According to a second aspect of the present invention, in the obstacle detecting device of the first aspect, the heat exchange structure takes in the outside air and forms a forced air flow along the lens barrel. Includes forced ventilation means.

According to a third aspect of the present invention, in the obstacle detecting device according to the first or second aspect, the heat exchange structure forms a cylindrical space outside the lens barrel and surrounds the lens barrel. A heat-insulating outer cylindrical body, and a flow channel structure that takes in external air into the cylindrical space and flows along the entire circumference of the lens barrel.

According to a fourth aspect of the present invention, there is provided an obstacle detecting device according to the third aspect, wherein the lens barrel is disposed on an entrance side of the lens barrel and blocks an inflow of outside air. The heat exchange structure has a plurality of openings in the lens barrel member at a position inside the infrared transmitting member, and a part of the air flowing through the cylindrical space flows along the inner wall of the lens barrel member. It includes a flow channel structure for flowing.

According to a fifth aspect of the present invention, there is provided an obstacle detecting apparatus.
5. A fan, wherein the forced ventilation means in the obstacle detection device according to 3 or 4 urges the external air taken in from an entrance side of the lens barrel to a depth side along the lens barrel, and a fan inside the lens barrel. An internal temperature detecting means for detecting the temperature of the cold junction of the thermopile element and outputting internal temperature information, and changing the output of the forced ventilation means in accordance with the external temperature information and the internal temperature information so that at least the background temperature is And cooling control means for increasing the output of the fan when the temperature becomes higher than the external temperature.

According to a sixth aspect of the present invention, there is provided an obstacle detecting apparatus according to the first aspect.
The angle at which the condensing optical system cuts the space above the thermopile element in the obstacle detection device according to 2, 3, 4 or 5 is defined as a half angle of sensitivity of the thermopile element.

[0015]

In the obstacle detecting device according to the first aspect, the heat exchange structure causes the temperature of the cold junction of the thermopile element to follow the temperature of outside air (outside air temperature) via the lens barrel. Infrared rays taken in from the outside are converged by the condensing optical system and irradiate the thermopile element, and the hot junction is heated to a temperature corresponding to the surface temperature of the obstacle. This temperature is lower than the surface temperature of the obstacle, but definitely higher than the outside air temperature. Therefore, an analog voltage corresponding to the temperature difference between the outside air temperature (cold junction) and the surface temperature of the obstacle (hot junction) is output from the hot junction of the thermopile element.

In the obstacle detecting means according to the second aspect, the forced ventilation means blows outside air to a member such as a lens barrel along an optical path of infrared rays reaching the thermopile element to promote heat exchange and reduce the temperature. Follow the temperature promptly.

In the obstacle detecting means of the third aspect, heat exchange between the outside air and the lens barrel is performed by utilizing the cylindrical space between the outer cylindrical body and the lens barrel. In addition, the outer cylindrical body that has been subjected to heat insulation, for example, blocks direct sunlight and heat sources in the vehicle body and the temperature and temperature changes of the device mounting part, as well as the barrel, and also blocks air taken in from the outside, These heats do not affect the temperature distribution of the lens barrel. The air taken in from the outside flows to the back side along the lens barrel, exchanges heat with the entire circumference of the lens barrel, and causes the entire lens barrel to immediately follow the external temperature. That is, in addition to mere heat conduction, the leveling of the temperature distribution of the internal structure and the following of the outside air temperature are achieved by the flow of air taken in from the outside.

In the obstacle detecting means according to the fourth aspect, air flows through the opening into the internal space of the lens barrel where the infrared transmitting member prevents the flow of outside air. Air taken in from the outside flows simultaneously outside and inside the lens barrel to perform efficient heat exchange. The air that has flowed into the lens barrel through the opening also exchanges heat with the light-collecting optical system and the support for the detection element, etc., and the air that enters from the outside reaches the detection element. The temperature is made to quickly follow the outside air temperature.

In the obstacle detecting means according to the fifth aspect, by the forced ventilation operation of the fan, much more air is involved in the heat exchange of the lens barrel than naturally relying on. Also, when the internal temperature rises relatively, for example, due to a sudden drop in the outside air temperature, the cooling control means increases the output of the fan to increase the amount of air involved in heat exchange, and Thermal neutralization.

In the obstacle detecting apparatus according to the first to fifth aspects, the noise signal of the detecting element is suppressed by "uniform temperature change of each part of the lens barrel" and "quickly following the temperature of each part of the lens barrel with respect to the outside air temperature". However, in the obstacle detection device according to the sixth aspect, the S / N ratio of the output of the thermopile element is maximized by optimizing the mounting relationship between the focusing optical system and the detection element. This SN
The ratio is a ratio between an analog voltage output from the thermopile element due to infrared rays taken in from the outside and a noise signal due to unnecessary infrared radiation.

In the obstacle detecting device according to the sixth aspect, the condensing optical system has a circular cross section, and conical focused infrared rays are incident from above the detecting element. The “angle θ that the light-collecting optical system cuts over the detection element” corresponding to １ ／ of the apex angle of the cone is set to the half-value angle of the sensitivity of the detection element. An angle θ smaller than this greatly reduces the amount of infrared light required to enter the detector. The larger angle θ is
The amount of unnecessary infrared rays incident from the lens barrel or the focusing optical system is increased at a rate higher than the rate of increase of the necessary amount of infrared rays incident on the detection element. This fact has been confirmed by experiments and is described in detail in the examples.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment will be described with reference to FIGS. FIG. 1 is an explanatory diagram of an obstacle detection device according to a first embodiment, and FIG.
FIG. 3 is an explanatory view of the structure of the sensing unit, FIG. 3 is an explanatory view of the structure of the thermopile, and FIG. 4 is an explanatory view of the relationship between the occupation angle θ of the reflecting mirror and the SN ratio characteristic of the thermopile in the first embodiment. 5
FIG. 4 is an explanatory diagram of a theoretical relationship between an input angle range of a thermopile and an SN ratio. In FIG. 2, (a) is a side sectional view, and (b) is a sectional view seen from the reflecting mirror side. 4A shows the directional characteristics of the thermopile, and FIG. 4B shows the SN ratio characteristics of the thermopile. 5A shows the directivity of the thermopile, and FIG. 5B shows the SN ratio of the thermopile.

Here, a concave reflecting mirror is provided at the bottom of the lens barrel,
At the entrance of the lens barrel, an infrared transmitting member for blocking the inflow of external air is arranged. The lens barrel has a large diameter of several tens of mm to several hundreds of mm, and infrared rays input through this diameter are focused by a reflecting mirror on an entrance window having a diameter of several mm or less of the detection element.

Here, outside air is taken into the space between the outer cylinder and the lens barrel, and is forcedly ventilated by a fan to exchange heat with the lens barrel. Further, the angle θ at which the reflecting mirror cuts out above the thermopile is set to the half value angle of the sensitivity of the detection element.

In FIG. 1, a sensing unit 10 detects infrared rays emitted from an obstacle (not shown) located on the left side in the figure. That is, the infrared rays radiated from the obstacle are made to be incident on the internal thermopile element 21 in a focused state,
An analog voltage corresponding to the surface temperature of the obstacle is output from the hot junction of the thermopile element 21.

The amplifier 11 amplifies the analog voltage output from the sensing unit 10. The A / D converter 12 converts the analog voltage output from the amplifier 11 into a digital signal to create infrared intensity information. The obstacle detection unit 13
The intensity information of the infrared ray is determined by referring to the output of the outside temperature sensor 32. If the temperature of the radiation source calculated from the intensity information of the infrared ray is higher than the outside temperature by a certain width or more, the radiation source is determined to be an obstacle, The alarm output unit 14 is operated. Alarm output unit 14
Notifies the operator of the presence of an obstacle through a buzzer or display (not shown).

The sensing section 10 has an internal temperature sensor 33 for measuring the temperature of the cold junction of the thermopile 21 in addition to the external temperature sensor 32 for measuring the external temperature. The temperature comparing section 15 compares the outputs of the outside air temperature sensor 32 and the internal temperature sensor 33 to calculate the temperature difference between the cold junction and the hot junction of the thermopile 21. The motor control unit 16 supplies power corresponding to the temperature difference to the motor 30 for driving the fan, and adjusts the flow rate of external air taken into the sensing unit 10 by the fan. That is, when the temperature difference increases, the output of the motor 30 is increased to promote heat exchange in the sensing unit 10.

In FIG. 2, the sensing 10 of FIG.
It has a double structure in which a cylindrical lens barrel 23 is held inside a cylindrical frame 25 lined with a heat insulating material. Frame 2
The cylindrical space between 5 and the lens barrel serves as a flow path for air taken in from the outside. The fan 29 driven by the motor 30
External air is taken into the cylindrical space from the air filter 27 side to form an air flow for heat exchange from the entrance side of the lens barrel 23 to the back side, and is discharged from the air filter 26 side. The air filters 26 and 27 are connected to the sensing unit 10.
Prevents trash and mist from entering the interior space.

The thermopile 21 is attached to a columnar support member 22 that crosses a lens barrel 23 with the infrared incident window facing the back. The thermopile 21 is held at a hollow position on the center axis of the lens barrel 23. The inner surface of the lens barrel 23 and the entire surface of the support member 22 are colored black to prevent reflection. The reflecting mirror 24 continuously arranged on the back side of the lens barrel 23 turns the infrared ray traveling inside the lens barrel 23 back to the entrance side and condenses,
The light enters the entrance window of the thermopile 21. Reflector 24
Is provided with an opening 36 having the same diameter as the thermopile 21 at the center thereof. The opening 36 functions as an exhaust port through which the air in the lens barrel 23 flows out, and also suppresses the Narcissus effect of the thermopile 21.

At the entrance of the lens barrel 23, a window plate 28 made of an infrared transmitting material (silicon, germanium, zinc selenide, etc.) is arranged. It is blocking. Radiation source (human body, etc.)
The infrared radiation emitted from the
The light travels inward and is condensed by the reflecting mirror 24 and enters the thermopile 21. The thermopile 21 detects a temperature difference between the hot junction heated by the infrared rays and the cold junction thermally connected to the lens barrel 23 and the like.

On the entrance side of the lens barrel 23, a plurality of openings 35 are formed at equal intervals surrounding the lens barrel 23. Part of the air taken in from the front through the filter 27 flows through the opening 35 into the internal space of the lens barrel 23 closed by the window plate 28. Then, after having exchanged heat with the inner surface of the lens barrel 23, the support member 22, the thermopile 21 and the like, it flows out through the opening 36 of the reflecting mirror 24.

A cap 31 made of the same material as the reflecting mirror 24 is disposed so as to face the opening 36 of the reflecting mirror 24. The cap 31 is a motor 30 for driving the fan 29.
And fixed to the thermopile 21 by the motor 30.
This prevents unnecessary infrared rays from entering from the side.

In FIG. 3, the thermopile 21 has a base.
The functional unit 66 is surrounded by a cap 62 and a cap 61. The function unit 66 includes a gold black 64 that is an infrared absorber,
Thermopile chip 63 which is an integrated circuit of micro thermocouple
It is composed of The thermopile chip 63 has its hot junction thermally connected to the gold black 64 and its cold junction thermally connected to the support 22 of FIG. The support member 22 follows the outside air temperature by the heat exchange structure described above. Therefore, when the infrared radiation emitted from the radiation source heats the gold black 64 to a temperature corresponding to the surface temperature of the radiation source,
The thermopile chip 63 outputs an analog voltage corresponding to a partial temperature difference of the functional unit 66, that is, a temperature difference between the support member 22 (cold junction) and the gold black 64 (hot junction).

At the top of the cap 61 of the thermopile 21, a silicon filter 65, which is an incident window for infrared rays, is arranged. Infrared light incident from the sky at an incident angle of inclination ψ through the silicon filter 65 is absorbed by the gold black 64 and forms a partial temperature difference in the functional unit 66. The incident inclination angle ψ is 0 ° when vertically incident on the functional unit 66, and 90 ° when horizontally incident from the side.

In FIG. 2, an angle θ corresponding to a half of the apex angle of the cone formed by the reflecting mirror 24 above the thermopile 21 is shown.
Is set to the half angle of the sensitivity of the thermopile 21. From this relationship, the diameter of the reflecting mirror 24 and the mounting position of the support member 22 (the thermopile 21) are determined, and the curvature of the reflecting mirror 24 is determined using the mounting position as the focal point position.

The angle θ is, in other words, the angle θ at which the reflecting mirror 24 cuts out above the thermopile 21, and is 1 / the angle range in which the reflecting mirror 24 is viewed from the thermopile 21.
Equal to 2. The half angle of sensitivity of the thermopile 21 is
The angle at which the sensitivity of the mopile 21 becomes 50%. Angle θ
Is the half-value angle of sensitivity, the influence of heat radiation by the lens barrel 23 and the reflecting mirror 24 is minimized, and the SN of the sensing unit 10
Maximize the ratio.

The S / N ratio of the sensing unit 10 is determined by the amount of infrared rays A from the human body and the like received by the thermopile 21
3. The ratio A / B with the amount of infrared rays B from the reflecting mirror 24 is meant. The relationship between the SN ratio and the angle θ was determined by computer simulation. This relationship will be described with reference to FIGS.

In FIG. 4A, the sensitivity T of the thermopile 21 is approximately 10 when the incident angle of incidence ψ of infrared rays is 10 degrees.
It is 0%, but drops sharply in the range of 10 to 50 degrees, and is 0% at 60 degrees or more. The half angle of sensitivity is 34 degrees.

For some combinations of the angle θ and the diameter of the reflecting mirror 23 (= barrel diameter), the SN ratio in the sensing unit 10 in FIG. 2 is calculated by using the relationship between the sensitivity T and the angle ψ. I do. The result is shown in FIG.

In FIG. 4B, the half-value angle 34 of the sensitivity of the thermopile 21 is obtained for any of the three types of lens barrel diameters.
When the degree is the angle θ, the SN ratio is maximum. here,
The signal S constituting the S / N ratio indicates the amount of infrared rays received from the thermopile 21 from a human body or the like, and the radiation noise N indicates the amount of infrared rays from the lens barrel 23 and the reflecting mirror 24. Each S / N ratio is 0 when the lens barrel diameter is 100 mm and θ = 28 degrees.
It is expressed as a relative value as dB.

One of the reasons why the directional characteristics (the relationship between the sensitivity T and the angle ψ) of the thermopile 21 shown in FIG. 3 becomes irregular as shown in FIG. The range of the incident inclination angle ψ is set to the silicon filter 65 or the cap 61.
Is limited. If the silicon filter 65 and the cap 61 are not provided, the relationship between the apparent area of the gold black 64 as viewed from the radiation source and the angle ψ is reflected as it is, and the directional characteristic of the thermopile 21 becomes the COS as shown in FIG. Curve. The half value angle of the sensitivity of the thermopile 21 having the idealized directional characteristics is 60 degrees.

Using the directional characteristics shown in FIG. 5A, the S / N ratio in the sensing unit 10 shown in FIG. 2 was simulated by computer. The result is shown in FIG.

In FIG. 5B, in the case of the thermopile 21 having idealized directional characteristics, if the angle θ is set to 60 degrees, the S / N ratio of the sensing unit 10 becomes maximum, and the amount of infrared radiation A from the radiation source becomes large. The influence of the infrared ray amount B from the lens barrel 23 and the reflecting mirror 24 can be minimized. Therefore, even in the case of the thermopile 21 having idealized directional characteristics, if the angle θ is set to the half value angle of the sensitivity of the sensor, the sensing unit 1 shown in FIG.
The reliability of obstacle detection at 0 may be maximized.

In the obstacle detecting device of the first embodiment configured as described above, the thermopile 21 is employed, and the cold junction of the thermopile 21 follows the outside temperature. , The analog voltage output from the thermopile 21 is basically zero. And since it is the structure which takes in air from the outside and heat-exchanges positively with the lens barrel 23 and the reflecting mirror 24, direct rays of sunlight are incident on the sensing part 10, and the inner surface of the lens barrel 23 etc. partially In the case where the temperature of the lens barrel 23 or the like temporarily rises from the outside temperature due to a sudden decrease in the outside temperature due to the outside temperature, The thermal noise level output from the thermopile 21 is suppressed to a low level.

Therefore, the sensitivity of the obstacle detection device is increased by reducing the reference value (temperature difference from the outside air temperature to be determined as an obstacle) in the obstacle detection unit 13 or increasing the gain of the amplifier 11. In this case, the obstacle detection unit 13 does not have to erroneously determine the thermal noise of the thermopile 21 as an obstacle. In other words, there is no fear of missing an obstacle having a low surface temperature or a distant obstacle as in the case where an easy method of ignoring noise output by expanding the reference value of comparison in the obstacle detection unit 13 is adopted.

The supporting member 22, the lens barrel 23, the reflecting mirror 24
Are made of the same metal material having high thermal conductivity, such as aluminum and copper, and are formed thin to reduce the heat capacity of the member.
Thereby, the surface temperature of each member quickly follows the outside air temperature by heat exchange with the taken-in air. The double structure of the frame 25 and the lens barrel 23 in the sensing unit 10 blocks direct sunlight and radiation from nearby undesired heat sources, and prevents a rapid change in the temperature of the lens barrel 23.

Further, the temperature comparison unit 15 and the motor control unit 16 shown in FIG. 1 are provided to increase the output of the motor 30 when the temperature difference between the outside air temperature and the inside air temperature increases, and to reduce the flow rate of air involved in heat exchange. Since the temperature is increased, the temperature of each part from the lens barrel 23 to the cold junction of the thermopile 21 quickly follows the outside air temperature. That is, even if the internal temperature becomes higher than the outside air temperature, the thermal noise due to the radiation from the lens barrel 23 and the like is not increased to the level of erroneous determination.

FIG. 6 is an explanatory diagram of an obstacle detection device according to the second embodiment. The obstacle detection device of the second embodiment is configured by replacing the sensing unit 10 of FIG. 1 with the sensing unit 40 of FIG. 6, and the components other than the sensing unit 10 of FIG. are doing. Therefore, FIG. 6 shows only a side cross section of the sensing unit 40 corresponding to FIG. 2A, and redundant description of the components other than the sensing unit 10 of FIG. 1 is omitted.

In FIG. 6, in the sensing section 40, a lens 48 for infrared optics is used as a light collecting means instead of the reflecting mirror 24 in FIG. Infrared light from a human body or the like is collected on the thermopile 41 by the lens 48.

In the second embodiment, the thermopile 31
Is a lens barrel 43 made of a material having high thermal conductivity.
Is connected to Further, each member from the lens barrel 43 to the cold junction of the thermopile 41 is air-cooled by the fan 49, and is always kept at the same temperature as the outside air temperature. Fan 49
The motor 50 is controlled in the same manner as in the embodiment of FIG. 1, and includes an outside air temperature sensor 52 provided on the outer surface of the frame 45 and an internal temperature sensor provided on the inner wall surface of the lens barrel 43. 53
Is controlled so as to always be the optimum rotation speed based on the temperature detection result.

The frame 45 is made of a heat insulating material, and forms a cylindrical space between the frame 45 and the lens barrel 43. The external air urged by the fan 49 flows into the internal space of the frame 45 through the air filter 47 on the inlet side, advances along the lens barrel 43, and is discharged to the outside through the air filter 46 on the outlet side. .

The lens barrel 43 is formed in a thin conical shape with a reduced heat capacity. The inclination of the inner surface of the lens barrel 43 is
8 is adjusted to the maximum angle α at which the infrared light condensed on the thermopile 41 is incident. The thermopile 4
The angle θ at which the lens 48 is viewed from the center of 1 is equal to the half-value angle of the sensitivity of the thermopile 41 from the analysis result of FIG. The inner surface of the lens barrel 43 is colored black to prevent reflection.

By these actions, as in the first embodiment,
The sensing unit 40 is an optical system in which noise caused by heat radiation of the lens barrel 43 does not matter.

In the first and second embodiments, a thermopile is used as an infrared detecting element. However, a one-dimensional sensor array or a two-dimensional image sensor that detects infrared light may be used. Thereby, the direction of the heat source can be detected together.

[0055]

According to the obstacle detecting means of the first aspect, since the detecting element is a thermopile element, it is strong and hard to break,
Less affected by garbage and moisture. Further, the function of detecting infrared rays can be exhibited only with a simple circuit configuration for amplifying the output voltage, and the overall circuit configuration can be easily reduced in size.

Further, since the temperature of the cold junction follows the outside air temperature through the heat exchange structure of the lens barrel, the thermopile element generates an output only for an object whose surface temperature is far from the outside air temperature. I do. Therefore, there is no need to cool the lens barrel, the peripheral circuit of the thermopile element can be simplified, and no complicated circuit adjustment is required. This makes it possible to detect obstacles with high reliability without a special cooling device, so that the entire system can be reduced in size and weight, and the structure for mounting the devices can be simplified.

Further, when the heat exchange structure includes forced ventilation means, since the followability of the temperature between the cold junction and the lens barrel is improved, a partial temperature rise of the lens barrel does not easily occur, and the temperature of the lens barrel increases. Is less likely to be erroneously detected as an obstacle.

In the case where the heat exchange structure forms a flow path structure between the outer cylinder and the lens barrel, the outer cylinder prevents the inflow of heat from the outside, so that an external heat source (direct sunlight, engine , A compressor, etc.), there is no need to worry about a partial temperature rise in the internal structure, and the difference between the cold junction temperature of each part of the internal structure and the thermopile element is reduced. Therefore, the level of radiation noise of the internal structure occupying the output of the thermopile element is suppressed, and even if the sensitivity of the obstacle detection device is increased,
It is not necessary to erroneously detect an obstacle. That is, the reliability of the obstacle detection device is improved.

In the case where an opening is provided in the lens barrel and air is branched into the lens barrel, heat exchange of air flowing into the lens barrel through the opening improves the followability of the lens barrel to the environmental temperature. In addition, it is not necessary to erroneously detect an obstacle even when the ambient temperature changes suddenly.

When the output of the fan is changed according to the difference between the outside air temperature and the inside air temperature, the output of the forced ventilation means is increased only when the possibility of erroneously detecting an obstacle increases. In other cases, power saving of the forced-ventilation means can be achieved while maintaining low output. In addition, because of the low output, the forced ventilation means does not need to be an unnecessary heat source for the detection element. Of course, the improvement in the followability of the lens barrel to the environmental temperature improves the reliability of the obstacle detection device.
Then, a small, lightweight, and inexpensive obstacle detection device can be provided by setting the sensitivity of the detection element to be high and reducing the diameter of the lens barrel by that amount.

Further, when the half of the apex angle of the cone formed above the thermopile element by the condensing optical system is set to the half value angle of the sensitivity of the thermopile element, the ratio between the output of the detection element and the noise signal is increased. Accordingly, the possibility of erroneously detecting a noise signal as an obstacle is reduced, and the reliability of the obstacle detection device is increased.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an obstacle detection device according to a first embodiment.

FIG. 2 is an explanatory diagram of a structure of a sensing unit.

FIG. 3 is an explanatory diagram of a thermopile structure.

FIG. 4 is an explanatory diagram of the relationship between the occupation angle θ of the reflecting mirror and the SN ratio characteristic of the thermopile in the first embodiment.

FIG. 5 is an explanatory diagram of a theoretical relationship between an input angle range of a thermopile and an SN ratio.

FIG. 6 is an explanatory diagram of an obstacle detection device according to a second embodiment.

[Explanation of symbols]

 10, 40 Sensing unit 11 Amplifier (conversion unit) 12 A / D converter (conversion unit) 13 Obstacle detection unit (identification unit) 14 Alarm output unit 15 Temperature comparison unit (cooling control unit) 16 Motor control unit (cooling control) Means) 21, 41 Thermopile (detection element) 22 Supporting material 23, 43 Lens tube 24 Reflector (condensing optical system) 25, 45 Frame (outer cylinder) 26, 27, 46, 47 Air filter 28 Window plate (infrared transmitting member) 29, 49 Fan (forced ventilation means) 30, 50 Motor (forced ventilation means) 31 Cap 32, 52 Outside temperature sensor (temperature detection means) 33, 53 Internal temperature sensor (internal temperature detection) Means) 35, 36 aperture 48 lens

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-82988 (JP, A) JP-A-2-234279 (JP, A) JP-A-3-67947 (JP, U) JP-A-53-947 158964 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01V 8/12 G01J 1/02 G01V 8/14

Claims (6)

(57) [Claims] 1. A detecting element for detecting the intensity of infrared rays, a converting means for forming intensity information of infrared rays from an output of the detecting element, and an infrared ray taken from the outside guided to the detecting element and input in a condensed state. An obstacle having a lens barrel and a condensing optical system, temperature detecting means for detecting outside air temperature and outputting outside temperature information, and identification means for judging an obstacle based on the intensity information and outside temperature information. In the object detection device, the detection element thermally communicates its cold junction to the lens barrel,
An obstacle detection device, comprising: a thermopile element for generating the infrared intensity output from the hot junction; and a heat exchange structure for exchanging heat of external air with the lens barrel. 2. The obstacle according to claim 1, wherein the heat exchange structure includes a forced ventilation unit that takes in the outside air and forms a forced air flow along the lens barrel. Detection device. 3. The heat exchange structure includes: a heat-insulated outer cylinder that forms a cylindrical space outside the lens barrel and surrounds the lens barrel; and external air is introduced into the cylindrical space. The obstacle detection device according to claim 1, further comprising: a flow channel structure that flows along the entire circumference of the lens barrel. 4. The optical system according to claim 1, wherein the lens barrel has an infrared transmitting member disposed on an entrance side of the lens barrel to block an inflow of external air, and the heat exchange structure includes an infrared transmitting member at an inner position of the infrared transmitting member. The obstacle according to claim 3, wherein a plurality of openings are provided in the lens barrel member, and a flow path structure that allows a part of air flowing through the cylindrical space to flow along an inner wall of the lens barrel member. Detection device. 5. A fan for urging the external air taken in from an entrance side of the lens barrel to a rear side along the lens barrel, wherein the forced ventilation means includes: a fan for energizing the thermopile element inside the lens barrel. Internal temperature detecting means for detecting the temperature of the cold junction and outputting internal temperature information; and changing the output of the forced ventilation means in accordance with the external temperature information and the internal temperature information, wherein at least the temperature of the cold junction is equal to the external temperature. 5. The obstacle detection device according to claim 2, further comprising: a cooling control unit configured to increase an output of the fan when the height of the obstacle is increased. 6. The thermopile element according to claim 1, wherein an angle at which the light condensing optical system cuts the space above the thermopile element is a half-value angle of sensitivity of the thermopile element.
The obstacle detection device according to 3, 4, or 5.